In a railway car, the primary suspension system generally refers to the suspension between the journal bearing assembly and the truck frame. The journal bearing assembly carries a wheel axle unit and acceleration forces generated by the wheel are directed to the primary suspension system with the forces being transmitted through the primary suspension system to the side frame. The secondary suspension system refers to the system between a bolster on the truck and the car body and generally include air or mechanical springs. The present invention is directed to primary suspension systems.
Past primary suspension systems have involved elastomeric rings surrounding the journal bearings. Such rings have included cut-away portions to provide softer spring rates and the cut-away portions were designed to provide desired vertical, longitudinal and lateral spring rates. Some of the primary suspension systems used heretofore are described in a patent to Egert 4,044,689, issued Aug. 30, 1977 and in a copending application, assigned to the same assignee as the present invention, of Eggert entitled "Primary Suspension System for a Railway Car", Ser. No. 348,446, patent no. 4,438,703 filed Feb. 12, 1982.
While the aforementioned systems have proven satisfactory for many applications, the spring elements are subject to wear. Also, the vertical, lateral and longitudinal spring rates are generally related to each other and cannot be independently adjusted.